This invention relates generally to artillery fuze radomes which are used for a protective structure for the electronic components located in the nose of such a fuze. Specifically, this invention relates to artillery fuze radomes ordinarily made from thermoplastic material. This invention is specifically related to the class of thermoplastic radomes wherein a metal cap is used in combination with a thermoplastic protective structure for a fuze.
First, thermoplastics are used as a manufacturing material for these artillery fuze radomes because of their desirable electrical and mechanical properties, low cost, and amendability to mass production. A major problem with thermoplastics is their limited ability to protect the fuze during flight from the combined effects of aerodynamic heating, and erosion due to rain, dust, and other dense materials within the atmosphere. Erosion of the radome due to these solid materials and rain causes degradation of the accuracy of the electronic fuze mechanisms for range findings or other significant damage to the electronic components therein.
Different thermoplastic radomes exhibit varying deterioration rates when subjected to dust or rain impingement. This deterioration can be delayed somewhat by increasing the thickness of the radome tip. However, military specifications with regard to artillery fuze radomes do not allow sufficient material to be added to the tip in order to survive the complete flight profile from the foremost gunfire conditions. A valid means for protecting thermoplastic radomes from erosion and degradation is to use a metal cap. Heretofore, these caps have been designed such that they were interior to the radomes.
Another solution to the problems of erosion, ablation and also triboelectric charging is to design the radome to be as strong and thick as possible at the tip. Unfortunately, this approach is good only for velocities below 3,000 feet per second. Above these velocities the meatal cap is usually necessary. The cap is usually imbedded in the plastic for protection against heat and charging. The limitation with this design is that the umbrella cannot be very large due to interference with the fuze performance, hence a large amount of supporting plastic cannot be provided and rain is capable of undermining the cap.
The invention described herein overcomes many of the disadvantages of the foregoing constructions. It is therefore an object of this invention to provide a new and novel protective structure for internal fuze components. It is yet another object of this invention to provide a new and novel protective structure for internal fuze components in combination with a plastic fuze radome wherein said metal cap may be placed on the outer surface of the plastic fuze radome without interference with the electromagnetic radiation pattern from the fuze antenna.
It is yet an additional object of this invention to provide a new and novel protective structure for internal fuze components which may be placed on the outer surface of the plastic fuze radome and provide a large umbrella and in addition avoid triboelectric charging.
It is still an additional object of this invention to provide a protective metal strap-cap structure strapped to the outside of a plastic fuze radome which is capable of providing protection from mechanical ablation in addition to acting as a heat sink and a shield against windstream stagnation pressure.